There is as much variety in hollow bodys as there is in solid body electrics. First off look for comfort, does the neck fit your hand and the body fit your body and does the weight suit you? Check the neck joint, be sure it has a tight and solid fit (bolt on) with no gaps. Tap on the body in several places and listen carefully for any rattles on the inside, aviod any that rattle. Consider the bridge, some have floating bridges which can be a pain to keep properly intonated, you don't have to bump them much to knock the intonation off. Decide in advance if you really need a tremelo tail or not. Check the body over much the same as you would an acoustic guitar, look for any cracks or loose bindings. Play it unplugged, a good hollow body will sound good without an amp. If you plan to use it for live gigs you might want to look into some semi-hollow body guitars, they aren't quite as likely to give you as much feedback problems.